Extensometer



R. L. TEMPLIN May 16, 1933.

EXTENSOMETER Filed June 16, 1930 2 Sheets-Sheet 2 .ulg

amm/m mf/M :WA mm @m M wrmzssgs Patented May 16, 1933 UNITED; STATES PAT-ENT OFFICE RICHARD L. TEMPLIN, OF PARNASSVUS, PENNSYLVANIA, ASSIG-NOR '1"0l ALUMINUM COMPANY OF AMERICA, OF lI-I'ITSZBURGI, PENNSYLVANIA, A CORPORATION PENNSYLVANIA Application led June 16,

My invention pertains to the instruments known as extensometers which are used for measuring the elongation of specimens under the tension applied by a testing machine or the like. One object is to improve upon eX- tensometers, as heretofore produced, in rel gard to precision. Another object is to pro- Vvide. an extensometer which can be attached to and removed from the specimen, when the latter is in place in the machine, with eX- ceptional facility. And other objects of my invention and advantages secured thereby will appear from the following specification taken in connection with the claims annexed thereto.

I have described by way of example in the following specification and shown in the accompanying drawings one form of eXtensometer in which my invention may be embodied, together with a modified form which one of the elements of the device may take. I wish it understood, however, that my invention may be embodied in other forms, and that changes may be made in the forms '1 l rig. e;

Fig. 6 is a section on the line VI-VI of Fig. 2;

Fig. 7 is a View of the spacing bar detached from the instrument; and

Fig. 8 is a. fragmentary view of a similar nature to Fig. 3, but showing a modified means of mounting and operating the speci` men-clamping means.

Referring to Fig. 1, the extensometer includes a post. a to the bottom end of which described and shown, without exceeding the nXTENsoMnTER 1930. Serial No. 461,382.

is rigidly secured a lower yoke b and to the Vtop end of which is pivoted an upper yoke c.

its ends, with jaws adapted to seize the specimen Ebetween-them. Thus the elongation, under the tension applied by the testing machine, of that portion of the specimen which is enclosed between the jaws' of the two yokes, will be shown bythe indicator d. y

Except in regard to the manner of their support'upon the post a. and the connections they carry for the indicator CZ, the yokes and c are substantially the same. Referring to the upper yoke 0, it includes a pair of parallel arms l() and 11 (Figs. 2 4) joined by a neck 12 at which is located the means for mounting the yoke upon the post a. The arms and 11 are threaded to receive hollow cylindrical bearing members 13 which are disposed opposite to each other and in which are slidably and rotatably mounted plungers 14.

The plungers 14 are formed at their inner ends with specimen-engagingand gripping means which, as shown, take the shape of flat jaws 15 vhaving V-shaped knife edges for engaging and gripping the specimen, though other forms of aws, such as the well known form employing sharp points, might also be used.

,The knife edges of the jaws are so disposed as to engage the specimen at diametrically opposite points, as may be clearly seen from Fig. 4. The outer ends of the plungers 14 are provided with stems 1G which extend through the bearing members 13 and terminate in knurled heads 17. Springs 18 are disposed between the plungers 14 and the ends of the bearing members 13 and tend to press the plungers strongly towards each other so that their jaws 15 will grip the specimen E firmly.

@ne of the features of the eXtensometer is the maintenance of its centering about the .axis of the specimen being tested, whereby the instrument is always substantially balanced about such axis and the leverage at which the indicator CZ is operated always remains the same. To this end, as well as to maintain the knife edges thereof diametrically opposite each other, the jaws 15 are con- Y opposite side.

nected by means of a pair of curved links 19 which are'pivoted together at one end, their other ends being pivoted to the jaws by means of the studs 20. The pin 21 by means of which the links 19 are pivoted together is extended upward and enters a slot 22 formed in a plate 23 which is secured to the neck 12 of the yoke. It will be observed from this that the links 19, by reason of the guiding of their pivot pin 21 in the slot A22, cause the jaws 15 to move together, and towards rand away from the axis of the specimen to the same extent, thereby maintaining a centering of the instrument about suclilaxis at all times. In addition, the links maintain the knife edges of the jaws 15 parallel at all times, regardless of the fact that the' plungers 14 carrying such aws can rotate in the bearing members 13, since it will be observed that the rotation of one of the plungers 14 will be directly imparted to its oppositely disposed plunger by reason of the links 19. This insures the maintenance of the knife edges of the jaws 15 in alignment at all times.

'Io separate the jaws 15, for applying the instrument to a specimen or removing the instrument, a pair of finger levers 24 are pivoted to the yoke, one at each side of the latter.

`The inner ends of these `finger levers are formed with flat hooks 25 `which engage beneath beveled lips 26 formed at the ends of the plungers 14, the hooks being retained in engagement beneath the lips by relatively weak tension springs 27.

The constructionis such that although the hooks 25, by their rengagement beneath the lips 26, will normally hold the jaws 15 in the horizontal position proper for engaging such aws with the specimen, nevertheless such holding is impositive A and the jaws can rotate about their axes whenv they are definitely impelled todo so, as would be the case when one side of the specimen should stretch to a greater extent than the Swiveling of the jaws about their axes under such conditions as the lastnamed is desirable, as in that way the reading given by the indicator d is the mean stretch of the specimen. By compressing theV finger levers 24 towards each other the jaws 15 are separated for applying the instrument to the specimen. The finger levers are then released, allowing the springs 18 to force the jaws, which willbe maintained horizontal at that time because of the engagement of the linger lever hooks 25 beneath the lips 26, against the specimen, the knife edges of the jaws engaging the Vspecimen at diametrically opposed points.

' The swiveling of the jaws 15 would, of itself, only allow for irregularity of stretching ofthe specimen alongtwo sides. In orr der to make complete provision for such irregularity of stretching, and to obtain a reading of the true mean stretch, I construct the upper yoke so that it can swivel about an axis at right angles to the axes of the jaws. To this end, the neck 12 of the yoke has threaded thereinto a stud 28 formed with a conical bearing portion 29 and a shank 30 the outer end of which is threaded. The shank 30 is rotatably mounted in a bushing 31 formed at each end with conical bearing surfaces (Figs. 2, 3 and 6), one for engagement bythe bearing portion29 of the stud 28 and the other'for engagemeiitby aconical' bearing'portion formed upon a nut 33 which is threaded upon 'the shank 30,"such nut,fafter adjustment for a proper rotative connectionr between the bushing 31 and the stud 28, being secured by means of a lock knut 34 and lock washer 35. It will thus be seen that 'the' upper yoke'itself can swivel about the axis` of the stud 28 while the jaws v can swivel about their own axes disposed at right angles to the axis of such stud, the re-v sult being that the jaws arecapableof universal movement. Inv this manner it is assured that the mean stretch ofthespecimen will be shown lby the indicator regardless of along what lines of the specimen any irregu.

larity of stretching occurs.

To connect the upper yoke pivotally with the post a the latter is provided withl an annular head 36 whichis split longitudinally, as indicated at 37. Pointed pivot screws 38 are threaded into the head 36`on the center line of the split and engageY hardened pivot lbearings 39 secured opposite each other in the bushing 31. A screw 40 passes through one part and enters the other part of the head 36 so that the split portions thereof Vcan be drawn together to clamp the pivot screws 38 after adjustment of the latter. The upper yoke c pivots about the screws 38 during the stretching of the specimen. The lower yoke b is formed with a collar-.41 V(Fig. 1) which surrounds the lower end. of the post a and is shrunk or otherwise rigidly secured thereon.

Referring again to the upper yoke, its arm 11 is extended and bent around .to provide a boss 42 which is disposed on aline passing through the axis that will be occupied by the specimen and extending at right angles to the pivotal axis of the'yoke. The boss is split, as indicated at 43, and is threaded to receive a thimble 44 formed with a bore 45 having at the lower end thereof a spherical seat to receive a ball 46 formed at the top end of a rod 47 which is connectedfto the indicator ci at the upper part thereof. The thimble 44 is adjusted, and then clamped in such adjusted position by means of a screw 48 passing throughone part and entering the other of the split boss 42. The adjustment is such that the center of the ball 46, when seated, will be in the same plane with the pivotal axis of the yoke and the specimen-engaging edges of the jaws 15. The

lower yoke t is provided with means for yoke.

ing taf 52 connecting the indicator d to it directly beneath the thimble carried by Vthe upper yoke, a suitable adjustment being provided, to allow of the proper pull being exercised by the rod 47. The indicator is provided with suitable means for setting it toA zero, and may be calibrated as desired, usually in inches of stretch per inch of the specimen.

When the specimen is under test the weight of the upper yoke will operate against the tension being applied by the testing machine, and although the parts of the instrument are vmade of aluminum where suitable, this would introduce an inaccuracy. To meet this condition I provide a helical spring GO (Fig. 2) which surrounds an abutment screw 49, the latter being threaded into a horizontal lug projecting from a bracket 5l secured to the head 36 on the post a. The spring is disposed between the lug 50 and the lower face of the upper yoke c, and is of such calculated strength as to bal-ance the weight of such In this way any inaccuracy of reading on the indicator d, due to the weight of the upper yoke, is ohviated.

The indicator is usually calibrated for use upon a determined length of the specimen being tested. Supposing, for instance, that this length yis ten inches, the instrument can be placed upon a standard rod having marks thereon which are precisely ten inches apart and the edges of the jaws of the upper and lower yokes be made to strike these marks with precision. Thereupon the screw 49 can be adjusted until it just engages the lower face of the upper yoke and locks in such adjustment. Thereafter the `jaw edges of the upper and lower yokes will always be precisely ten inches apart when the upper yoke is resting upon the screw 49.V

As another means of setting the instrument to the standard distance, and also as a means for holding the parts securely in place when the instrument is not in use, I provide a spac- (Figs. l and 7) adapted to engage between the upper and lower yokes and to be .secured in place by screws 53 passing through said yokes and'entering said spacing bar. The bar may be of such length that when engaged between the yokes, the knife edges of the jaws carried by such yokes will be spaced the required distance apart.

It will `be noted that each yoke is broadly in the shape of a rectangle having one corner open, thereby permitting the instrument to be placed on the specimen while the latter is in place in the testing machine, all that is necessary being to manipulate the finger levers so as to separate both pairs of jaws and then allow the jaws to close upon the specimen while the upper yoke is resting upon the screw 49. It will be seen, further, that the construction of the instrument is balanced in that the jaws 25 and associated parts, as well as the portions of the yokes vcarrying them, vare balanced against each other across the axis .of the specimen. Likewise the indicator cl and associated parts are balanced against the post a, linger levers 24, etc.,- across the axis of .the specimen. The weight of the parts are calculated to obtain Vthis balance-as nearly as possible thereby to avoid .any material tendency of the instrument to cant upon the specimen, which canting, if. permitted, would tend to introduce In the instrument shown the leverage at which the indicator operates is two to one,- i. e. the distance between the center of the ball 46 on the rod 47 connected with the indicator and the pivotal axis of the upper yoke is --twice that between such pivotal axis and the axis of the specimen. The leverage may, of

course, be designed as desired, but, whatever it may be, such leverage is preserved by the centering character of the jaws, requiring that the axis of the specimen be located always at the same point.

In the construction heretofore described the specimen-engaging jaws are automatical-v lyself-centering. In Fig. 8 there-is, shown a form of the instrument in which the centering of the jaws is obtained by an adjustment instead ot automatically. In this form, one

`.ot the jaws, designated-15a, is yrotatably `locks the nut 57 in position when the latter has been adjusted for a proper rotative connection between the sleeve 54 and the shank 58 and its associated parts. Thejaw 15 opposite to the jaw 15a is constructed and mounted similarly to the jaws of the construction shown in Fig. 3 and is operated by a linger lever 24 as in such figure. The jaws 15 and 15a are connected by links 19awhich are similar to the links 19 except that the pivot pin connecting the links is not extended and the slotted plate 23 isomitted. The links 19a, in this embodiment of the invention, serve only to maintain the aws l5 and v15a in line with each other.

In the use of the instrument, when constructed in accordance with Fig. 8, the sleeve 54 is adjusted so that when the jaw 15a; en-

gages tlie specimen, the axis of the-latterwill be centrally disposed with respect to the instrument. 'Ihe centering of specimens diifering in diameter is thus obtained by anadjustment, instead of automatically :as-in the embodiment first described. The instrument asv is, however, quite convenient to use where the specimens do not frequently vary in diameter. lt is applied to the specimen equally .as easily as in the form previously described,

jinsures that the axis of the specimen is always at the same location, thereby maintaining constant the leverage at which the, in-

strument operates, and by the counter-balancing of the weight of the pivoted yoke.A In

addition to the advantages of extreme accuracy which results from these features and from the capability which the specimen-engaging jaws have of universal movement and the insurance .that these jaws engage the specimen at diametrically opposed points,

the instrument has the material further advantage that it is exceptionally easy to attach to the specimen whenthe latter is in the testing machine, especially, where the specimens vary in diameter, in the case of the automatically centering form shown in Figs. 2 4; Moreover, the instrument is easy to set to a predetermined test length of specimen, is rugged and not liable to get out of order, and is of struction.

1. An extensometer comprising'a `pair of spaced yoke members pivotally mounted to have universal movement with respectto each other, indicating means connected between said yoke members attheir other ends,

and self-centering specimen-engaging means carried by said yoke members intermediate Vtheir ends, whereby the extensometer is bali anced about the specimen.

2. An extensometer comprising a. support, a member movably associated with said support, a second member associated with said support, indicating means connected between said members, and self-centering specimenengaging means carried by each of said members and disposed intermediate said support and said indicating means, whereby the extensometer is balanced about the specimen.

3. An extensometer comprising a support, aV member pivoted adjacent one end to said support, a second memberlixed adjacent vone `enel to said support, indicating means ccnnected between said members adjacent the ends thereof remote from saidsupport, and self-centering specimen-engaging means carried by each of said members intermediate .their ends, wherebythe extensometer is balanced about the specimen.

e. An extensometer comprising a yoke, op-

vpositely disposed self-,centering jaw members `individually rotatable in said yoke, and

means for maintaining said jaw members in alignment with each other.

5. An extensometer comprising a support,

`a jaw-carrying yoke rigidly attached to said support, a member pivoted to saidy support,

a second yoke rotatably mounted in said pivoted member, and' self-centering jaw members individually rotatable in said secondnamed yoke.

6. An extensometer comprising a support,

alignment with each other.

7. An extensometer comprising'a yoke, op- -positely disposed jaw vmembers individually rotatable in said yoke, yand links pivoted to each other and to said jaw members to maintain the latter in alignment.

8. An extensometer comprising a support, a jaw-carrying yoke rigidly attached to said support, a member pivoted to said support, a second yoke rotatably mounted in said piv.- otedmember, oppositely disposed j aw members individually rotatable in said secondnamed yoke, and links pivotedto each other Vand to'said jaw members to maintain they latter` in alignment.v a simple and economical con- 9. An extensometer comprising a yoke, a jaw member carried yby said yoke, a second jaw member disposed oppositev the first and movably mounted-'in saidyoke, means tending to move saidl second-named aw member towards said first-named jaw member to clamp a specimen between them, and manually operable means for moving said secondnamed jaw member away from said lfirstnamed jaw member.

10.*An extensometer comprising a yoke, a jaw member mounted for rotation in said yoke, a second jaw member disposed opposite the rst and mounted Jfor rotation and longitudinal movement in said yoke, means tending to move said second-named jaw inember towards said rst-named jaw member to yclamp a specimen between them, and manually operable means for moving said secondnamed jaw member away from said firstnamed jaw member.

. 1 11. An extensometer comprisingv a yoke, a

jaw member mounted for rotation in said yoke, a second jaw member'disposed opposite the first and mounted for rotation and longitudinal movement in said yoke, means tending to move said 'second-named jaw member towards said first-named aw member to clamp a specimen between them, manually operable means for moving said secondnamed jaw member away from said rlirstnamedjawmember, and means for maintaining said jaw members in alignment with each other.

12. An extensometer comprising a yoke, an Jaw member' mounted for rotation 1n said.

yoke, a secondjaw member disposed opposite the first and mounted for rotation and longitudinal movement in said yoke, means tending to move said second-named aw member towards said first-named jaw memberk to clamp a specimen between them, manually operable means for moving said secondnamed jaw member away from said firstnamed jaw member, and links pivoted to each other and to said jaw members to maintain the latter in alignment.

13. An extensometer comprising a yoke, a jaw member carried by said yoke, a second jaw member disposed opposite the first and movably mounted in said yoke, means tending to move said second-named jaw member towards said first-named jaw member to clamp a specimen between them,-and a manually operable lever pivoted to said yoke and engaging said second-named jaw member to actuate said jaw member and release said specimen.

14. An eXtensometer comprising a yoke, a pair of oppositely disposed jaw members individually rotatable in said yoke, and means for impositively maintaining said members in a predetermined position of rotation. Y

15. An extensometer comprising a yoke, a pair of oppositely disposed jaw members individually rotatable in said yoke, means for maintaining said jaw members in alignment with each other, and means for impositively maintaining said members in a predetermined position of rotation.

16. An extensometer comprising a yoke, a jaw member mounted for rotation in said yoke, a second j aw member disposed opposite the first and mounted for rotation and longitudinal movement in said yoke, means tending to move said second-named jaw member towards said iirst-named jaw member to clamp a specimen between them, and manually operable means for moving said secondnamed jaw member away from said irstnamed j aw member, said last-named means comprising a lever having a flattened portion adapted to engage a beveled portion of said last-named jaw member to maintain said jaw member impositively in a predetermined position of rotation.

17. An extensometer comprising a yoke, a jaw member carried by said yoke, a second jaw member disposed opposite the first and movably mounted in said yoke, said secondnamed jaw member being provided with a bevelled lip, means tending to move said second-named jaw member towards said firstmember and normally maintaining it impositively in a .predetermined position or rotation.

v18. An extensometer comprising -a yoke, a'k

jaw member carried bysaid yoke, a second jaw'member disposed opposite .the first and movably mountedrin said yoke, said secondnamed vjaw membenbeing provided with a bevelied lip, means tending to move said second-named towards said first-named jaw member .to clamp a specimen between them, links pivoted to each other and to said jaw members for maintaining the latter in alignment, and a manually operable lever pivoted to said yoke and engaging beneath said lip for actuating said second-named jaw member and normally mainta-iningy it impositively in apredetermined position of rotation.

19. An eXtensometer comprising a yoke, a pair of jawV members mounted in said'yoke or'movement with respect to each other, and

means for equalizing the'movement of said jaw members.

20An eXtenvsometer comprising a yoke, a

pair of jaw members mounted in said yoke for movement with respect to each other, links pivoted vto eachother and to said jaw members, and a guiding member on said yoke Vassociatedwith said links at the pivotal con.-

nection of thelatter, thereby to equalize the movements of said jaw members. f 21. VAn'eXtensometer comprising a yoke, a pair of jaw members mounted in said yoke for rotation and movement with respect toy each other, means for maintaining said jaw members in alignment, and means for equalizing the movements of said `j aw members.

22. An extensometer comprising a yoke, a

pair of jaw membersmounted infsaid yoke for rotation and movement with respect to eachother, links pivoted to each other and to said j avv members, anda guiding member-on said yoke associated with said links at the pivotal connection of the latter, whereby said links maintain said jaw members in ment and equalize their movements.

23. An extensometer comprising a yoke, a

pair of jaw members mounted in said yoke for movement with respect to each other, means tending Ato move said Jaw members towards each other tov vclamp-a specimen, manalignually operable means for separatingsaid jaw i members, and means for equalizing the movements of said jaw members. Y

24. An extensometer comprising a yoke, .a pair otjaw members mounted' in said yoke for movement with respect to each other, means tendingto move said jaw members towards each other Vtor-clamp a specimen, a pair of manually operable levers pivoted to said yokemrand engaging `said jaw members, and

means for equalzng the movementsr of said Jaw members. v i y Y t 25. An veXtensometer comprising a yoke, a'

pair ofrjaw members mounted in said yoke for rotation and movement with respect to each other, each of said j aw members being provided with a bevelled lip, springs impel-v ling said jaw members towards each other to i clamp a specimen, and a pair of manually operable levers pivoted tosaid yoke, and engaging beneathV saidjlipsgv for actuating saidV j aw members against saidsprings and maintaining said jaw members in a predetermined position of rotation.

*26. An extensometer comprising afyoke, aL pair of `jaw members mounted in said yoke for rotation and movementjwith respect to each other, each of said-jaw members being provided with a bevelled lip, springs impelling said j aw members'towards each other to clamp a'specimen, a' pair 'of manuallyoperable levers pivoted' to saidyoke, and engaging beneath said lips, for actuating saidjaw membersfagainst said springs and maintaining said jaw members in a predetermined position of rotation, and means for'equalizing the movements of said jaw membersf 27. An extensometer comprising a'yoke, a pair of j aw members mounted in said yoke for rotation and movement with respect Ito each other, each of said jaw members 'being Y provided with the bevelled lip, springs impel- `ling said jaw members towards each other to,k clamp a specimen, a pair of manually operable levers pivoted to said yoke, and engaging beneath saidlips, for actuatingsaid )awV endY with i a socket. f

"30. 'extensomet'er comprising a yoke memberfor engaging a specimen, a second yoke member for engaging the specimen above the rstfa supporting-'member having said yfirst mentioned yokejmember rigidly attached',

thereto and/having the second yoke member pivotally attached thereto, an indicator connected between said yoke members, an adjustable"abutment4 carried by one of saidyoke members and engaging the other, thereby to y determine the distance'of separationot saidv yoke members,'and a spring interposed between thesecond named yoke member and the support thereforto balance its weight. In testimony whereof, I sign my name.

f RICHARD L. TEMPLIN.

'ball for cooperation v'with said separated points, a support member having Y one of said yoke members rigidly attached thereto andhaving a second yoke member pivotally attached thereto, an indicator connected with one ofsaid members, and a ball i and socket connection between said indicator and the other yoke member. Y f Y 29. An extensometercomprising Va pairvof yoke members for engaging Sa specimen at separated points, a support member having one of saidryoke members rigidly attached thereto'and having the-second yoke member pivotally attached thereto, an indicator connected with one of said yoke members, a' socket 4 adj ustably associated with the other yoke member, and a link connected at one endf 'A f' with said indicator and providedat the other i'io CERTIFCATE F CRRECT.

Patent No. 1,908,930. May 16, 1933.

RECHRD L. TEMPLIN.

it is hereby certified that error appears in the printed speciiicatien of the aiiove mimbereii patent requiring correction as follows: Page 5. line 71, claim 17, for "or" read "oi"; and line 91, claim 19, ier "movement" read "movements; anti that the said Letters Patent sheuid be reed with these corrections therein met the same may conform to the reoord oi the case in the Patent Office.

Signed and sealed this 27th day of June, A. D. 1933.

M. J. Moore.

(Seal) Acting Commissioner o Patents. 

